Underreamer



Dec. 28, 1948. R, C, BAKER 2,457,628

UNDERREAMER Filed June 17, 1942 Y 2 Sheets-Sheet 1 gmx w'mw m .n/SEN C. BAKE/e',

INVENTOR.

1.4 TTORNEY S.

Patented Dec. 28, 1948 UNITED STAT EsA l.miTI-11$1-1T OFFICE UNDERREAMER meen o. nem. ooaimr'a. assigner to Vernon,1Cal iI., a corpora Baker Oil Tools, Inc., tion oi' California Appleman June 1v, 194,2. serial No. 44u92' It is'an object oi the present invention to prcvide en improved imderreamer especially adepted for operation in herd formations having roller cutters that can be held positively in expanded position in such manner as to prevent the reactive force ofthe formation on the cutters from. moving them inwardly to e position oi.' smaller cib lectivo diameter.

A further object of the invention is to provide an improved underreemer having roller cutters positively held in expended position, whose extent or outward expansion is positively limited.

Yet another object or the invention is to provide an improved underreamer employing roller cutters held in expanded position by the drilling weight imposed upon the tool.

Another object of the invention is concerned with the automatic retraction oi' the roller cut ters oi an underreumer by the simple expedient of raising or elevtinsr the drilling string towhich the underresmer is attached.

Yet another object or the invention resides in the provision oi an improved hydraulically expansible roller underreemer or sturdyr end simplliled construction,.capa.ble oi' efficiently opereting upon a. shoulder formed in comparatively linz-d iormations, for the purpose or materially enlersins the well bore below a. casing shoe.

This invention has other objects that will become apparent from a consideration of the embodiment shown in the drawingsaccompanying `und forming part o: the present speciiication.

'.lhis` form will'now be described in detail to illustrate the 4general principles of the invention, but it is to be understood that auch detailed descriptlon is not to be teken in a. limited sense,

since the scope of lthe invention is best dened by the claims appended hereto.

Referring to the drawings:

Figure l is a. longitudinal section through an hydraulically expenslbleroller underresmer. with Acertain parte in retracted position to enable free passage or the tool through e well casing:

Fig-ure 2 is s view on en enlsrged scale of part of the device. teken generally along'the line 2-2 in Figure 1;

Figure 3 is e. view similar to Figure 1, disclosing the underreamer cutters and associated parte in expended position;

Figure 4 is a cross-section teken 8.10m; the line I-l in Figure l;

4 claims. icl. ess-1e) 1 2 Figure sie u cross-section taken along the li-S in Figure 3: and

Figure 6 isa. bottomplan view of the pilot portion oi the underreexner taken along the line i-B les In` its 'general especie, the invention is concerned with sn underreemer that can be'low'ered i through a. weIi casing with. 'its roller cutterst'in retracted position, to enable thev tool topass readily throughzthe casing to any required position in an open wellbore below'the casing shoe. iWh'en thisposltion is reached.l thelsupportlng' members for the roller cutters are elevated hydraulically and caused to ride up inclined or cam expender portions on the meinbody o: the underreemer to force the roller cutters radially outwardly for enlarging the well bore in excessoi the inside diamveter oi the casing through whiohthe tool 'hes passed In a preferred form, the rollers are such as to rst iorm'a shoulder in the 4formation and then operate upon this shoulder toedect the .sir-ed increase inthe diameter-of the bore hole.

The supporting members and associated roller cutters i expand outwardly upon their upward movement to nposition inwhioh the reactive force of the well of the formation on the'rollex-.cutters and supporting members is transmitted directly to the main body or the underreemer in such manner as to positively Iii-event` the 'outwardly expended members from moving inwardly. lAs a result, the roller cutters temoin in fully expanded condition ter the purpose or enlarsine'tlie-boro hole to the speciilcd diameter. in thisexpnnded position. the drilling weight on the tool is imposed 'directlyl on the roller4 cutters through their supporting members, thereby relieving mdny ofthe imderreamer parts from `the load. The extent of outward expansion ofthe roller cui... ters is also preiersbly limited by .engasement of the supporting]r members with nV suitable abutment formingpart of the underreamer. The net result of transmitting lthe drilling weight directly through the simportins members. positively preventing their inward movement fromexpanded position, and positively preventing their outward movement beyond the maximum expanded position desired, effectively locks them undI their associnted roller cutters in expanded position, resulting in an extremely sturdy and rigid underrentner capnbleoi enlarging the diameter of a well bore drilled through comparatively hard forms.- tions. The underreamer is so constituted that the drilling weight maintains its cutters in expanded position, which force is supplemented by decussa e I"rmi action aus moves the-inks 'so autosport ling members 42l ux.\'iivitrflli'7- to outward e2- Yp'ansion of 'the supporting members and roller cutters 2B. 'As the cylinder head B1 'moves upwardly within ene-bore l: orthe'mainbodri the can escape between vthe latter and the wash pipellil i4. since there is no seal therebetween.

The pressure necessary to' move the cylinder 5 5 in aniupward direction so as to-produce out'- ward expansion o-tbe roller cutters my be obtainedina number of ways. In the' present inl`stance. the ow oi'V iluid from thebottomy end of 1,the wash pipe Il is restricted so as'to build upa taci; pressure therein of-suilicientvalue to elevate fthe cylinder i'and hold it in such elevated lposition so long as a sufcient quantityjoi.' drilling mud is being Dumped through the tool. The uid `exitsirom the wash pipe |4- through nozzles 12 adapted to directcleanlng iiulid on the cutters :if .and through va comparatively small central 'passegelljin' the lower end of vthe body, which de `liversiluid to lower nozzles 14` capable of directing it onto pilot blades 15 at the lower end of the'body I0. The openings through all Voi.' these nozzles 12. il are of a lesser combined ares. than the internal area of the wash pipe i4,V in effect producinga' l. combined restrictionV to the passage or fluid in the "nature oi' an orifice capable of building up a back pressure in the' fluid within the wash pipe I4 and cylinder s pace E4 more than-sumclen't to elevate 'the cylinder 55: ,A

' f The tool is run 'through-tbe casingnAonuthe 'end oi a string oi drill 4pipe with 'the parts in retracted position. as shownin' Figure 1. The

" supporting members 21 arein their. innermost `position, with the roller cutters 26 contained within the side pockets and grooves i2. When in such position the inner shoulders 42 engage the projections 2l, andthe cylinder iS'is in its -iowermost position with its'head 51 adjacent the piston .'iii. Upon reachingV the desired location "below-the casing shoe B: rotation -of the tool is started and drilling mud is pumped 'down the drilling string. Due to the 'ilow "restrictions -oileredby the various nozzles 'i2-, 14'fthe pressure of the iluid in the wash pipe--andcylinder space is increased to urge the cylinder 65 in im upward each supporting member rides upon the upwux'i'llyY diverging expander surface or cam 24; the supporting' member 21 and the roller cutter 26 begin .enlarging the well bore. As the borediameter increases. the cylinder iii continues toi move upwardly-, to shift the supporting `members upwardly to a corresponding extent along their cam surfaces 24 and the rollers 42B radially outwardly. The eiiective hole enlarging diameter of the roller cutters is thus increased until 'the maximum lateral outward diameter islreached, in which the straight faces or surfaces 16 on the supporting members engage the straight longitudinal stops or abutments 23 on'the body projections 2l. The limit ci' this upward movement is positively determined by engagement of the upper shoulder 4I on the supporting member with the body por- -tionorfilangei48 defining the upper end of the longitudinal groove'i 2. When in this position, it is preferred that the longitudinal bevelled sur- -Iaces 49 of the arms contact the wash pipev I4 so f asA to limit the outward movement ci lthrollercutters 26.'

-Withtbe cutters in this outward position. it is S-apparent-thatthey haveenlarsed the well bore ft'o form a shoulder'on which the teeth ot the roller -cuttersrcahoperate as the lmderreamer is rotated. Once this shoulder is formed, the required drilling weight is imposed on the cutters and the 'tool-gradually lowered as the formation shoulder tion material and effective -for maximum penel 7 tration into' the formation shoulder.

With the tool performing its undeneaming operation as a result `of its outward expansion, it is to be noted that the drilling weight on the cutters 2i is imposed directly upon them through the supporting members 21, because of the engagement of the upper shoulders 4I with the `mainbody of theftooll Moreover, the drilling torque-is transmitted directly from the body I0 to' the'supporting members 21 by engagement of the groove sides 29 with the sides 28 of these' members. It is turtherto be noted that the force of the formation tending to vmove the cutters 26 and supporting members 21 inwardly to a smaller effective diameter is-reslsted through engagement of the longitudinal surfaces 16 of the supporting members with the'- longitudinal surfaces or abutme'nts 23 on the body projections 2|. These two surfaces 18, 23 are substantially parallel to the tool axis-so that there is 4no component ol torce fjetleotiv'ei to move the supporting members 21 downwardly along their expander-s 24 and back .i to retracted position. Once the cutters have been expanded, they will be retained in that position by the drilling weight and the cooperation be- I tween the surfaces 16, 23. This maintenance ol the cutters 26 in outward position is assisted by 'the hydraulic iluid force tending to keep the cyl- 4indexbl, and also the cutters,in elevated position. :Alter the hole has been underreamed or enlarged to the required length. the pumpingaction isdiscontinued and the drilling string and unresistance oi.' the cutters 26' against the wall or the` hole tends to prevent their. upward movement.

'f resulting in the elevation of the main body I Il and wash pipe |'4 without a. corresponding elevation of the supporting members 21 and their associated links 50 and cylinder It. The abutment surface 23 of the body projections 2i are;

thereforez'pulled upwardly within the recess 44 in the supporting members. allowing the latter to move relatively in s downward direction along the inclined expander surfaces 24 and inwardly to a retracted position within the body Ill. The

extent of this relative downward and inward movement of the supporting members and roller cutters is limited by engagement of the inner l shoulders 42 with the projection shoulders 22 with respect to the piston 58 to its initial position.

' In theV event that the frictional resistance oil'ered by the wall oi' the well bore is insuclent to effect retraction of the supporting members 21 and rollers 28 into the contines of the under- REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Miller Feb. 12, 1924 Blanchard Aug, 4, 1925 Crum Mar. 18, 193i) Strang Apr. 15, 1941 Spink Sept. 9, 1941 

